A. Field of the Invention
The present invention relates to lighting systems, and in particular, to concentrated light sources and reflectors.
B. Problems in the Art
Over the years a wide variety of different types of lighting fixtures have been developed for a variety of different lighting purposes. In the case of lighting relatively large areas, it is conventional to utilize concentrated lamps and to surround them with a reflective material to gather and direct light energy from the lamp in a desired direction. One or more of these combined light sources is then directly aimed towards the area to be lighted.
Light energy spreads over distance. The illumination of a remote area therefore varies inversely as the square of the distance from the light source. Additionally, light fixtures directing light to a relatively large target area are usually many times smaller than the area to be lighted. The beam of light energy produced by each fixture most times must therefore cover a substantial area.
These characteristics present certain lighting problems. First of all, to maintain a given light level at a distant target area, the light source must produce a much higher level of light energy at the source. This can contribute to glare problems for those viewing the fixtures. Secondly, the use of diverging or converging beams generally results in a significant amount of light falling outside the target area. This results in spill and glare light. Spill and glare light are inefficient use of the light and are frequently objectionable. Spill light is the illumination of non-targeted areas. Glare light is the relatively bright luminance viewed when looking towards the light source.
An example of these problems can be illustrated by referring to conventional sports field lighting. Sports fields such as football fields, softball fields, baseball fields, or the like, constitute large areas. Not only must the two dimensional area of the field be lighted to a sufficient level for playability, a third dimension, the substantial volume of space above the field, must also have a minimum amount of light for playability. One solution would be to basically place vertical walls of individual fixtures on opposite sides of the field so that light would fill up the space between the walls to create the necessary light values throughout the three dimensional volume. This, of course, is impractical and virtually impossible. Therefore, a conventional solution has been to place several large poles in spaced apart positions around the field. Clusters of a number of light fixtures are placed at the top of the pole. Fixtures are aimed in various directions to try to fill up tile volume to be lighted, and fill it up in a way to maintain a suitable light intensity through the volume.
To accomplish this very high intensity lamps and very efficient reflectors are required. As discussed previously, this presents glare and spill problems as the lights, of necessity, are generally angled down towards the field, players, spectators, and surrounding areas. The light emitted from the face of conventional reflector systems for high intensity lamps forms generally an output of a constantly expanding hemisphere, generally of greater intensity at more central locations of the hemisphere and of decreasing intensity at outer edges. This output is of such a shape and size, however, that it can not be precisely limited at the edges of the volume defining the playing area, and therefore light spills outside the volume. In other words, light emanating from an elevated light fixture on a pole at a remote distance from the playing space generally will have higher light values at the center of the expanding hemisphere of light radiating from it. Thus, to create approximately the same light values at the edge of the playing space as in the center, requires the light energy from a number of the fixtures to be aimed so that the high intensity center portion of the radiating hemisphere is directed towards distance points of the space. Of necessity, this means that even if the more intense areas of the light energy are maintained in the target space, at least portions of some of the less intense areas away from the center of the radiating hemispheres will fall outside the playing space creating glare and spill light problems.
Another example is automobile racetracks. For cars traveling at very high speeds at night, a high level of light is needed at and immediately above the track for safety considerations as well as for viewing considerations. In today's world, also, the ability for television to produce a high quality picture at night for such events is also a prime consideration. Although only the track needs to be provided with this high level of light, economic considerations and conventional technology generally results in a lighting solution similar to that used for athletic fields. Individual lighting fixtures are clustered on as few light poles as possible, spaced around the track either on the infield side or outside the perimeter of the track or both. The fixtures are angled downwardly in different directions to try to direct enough light to the track to meet lighting requirements all the way along the track, some being a mile or more in length. Such lights, especially when installed on the infield side, cause glare to spectators positioned around the outside of the track, or conversely lights outside the track can cause glare for spectators in the infield or outside the opposite side of the track. Still further, spill light outside the track itself is substantial. Additionally, poles around the infield side of the track constitute visual obstructions to spectators and television cameras.
Many times lights are installed on the inside of a race track to better illuminate the track (many times banked inwardly), assist spectators' view, or illuminate the cars in the same direction as television cameras are viewing the cars. These lights are essentially aimed in the wrong direction at shallow angles with respect to the spectators, causing glare for the spectators outside or on the opposite side of the track from the infield.
Additionally, conventional grouping of lights on top of light poles causes large shadows. If lights for lighting the track could be spaced closely together it would eliminate or substantially diminish any shadows. Additionally, closely spaced lights could fill in lights between race cars as they are running on the track. This could be beneficial for spectators to more clearly see and differentiate between the cars, as well as help drivers as they draft other cars. Drafting involves driving directly behind a car, only inches away, even though traveling at great speeds. Such lighting would therefore be very beneficial. Such closely spaced lighting is simply not economically feasible when using lights elevated on poles.
The control of high intensity light sources by elevating them in clusters on poles or other structures, to allow the aiming and alignment of the fixture to reduce spill or glare is costly because structures become substantially more expensive as they become taller. Higher mounting heights on structures of lighting fixtures also creates additional maintenance problems and objectionable visual problems as the lights become visible from greater distances.
These are the types of problems (by no means inclusive) involved in this type of lighting. Again, the problems are primarily caused by the lack of ability to control light and glare because of the factors involved in lighting wide areas and volumes of space.
Problems also exist because of the inherent nature of conventional lighting fixtures. There is only so much light that can be generated from a single light source. Without a primary reflector such light is difficult to control at all. Even with a primary reflector, the inherent nature of light results in diminishment of intensity over distance and spreading of light with distance. There is only so much light that can be generated and applied to an area or a volume of space from one fixture at any given location. This also applies to utilizing plurality of individual lighting fixtures, especially when they are clustered on the top of poles. Also, the control of light from conventional fixtures can be difficult, including control of problems such as glare and spill light.
Therefore, there is a real need in the art for a system which can improve upon the deficiencies of conventional large area lighting or solve some of the problems involved in large area lighting.
It is therefore a principle object of the present invention to improve upon at least some of the deficiencies in conventional lighting systems and solve some of the problems involved with the same.
Another object of the present invention is to provide a means and method for highly controllable lighting which provides flexible and precise control of light to a target area or three-dimensional space.
Another object of the present invention is to provide a means and method as above described which allows light energy to be used much more efficiently and effectively.
Another object of the present invention is to provide a means and method as above described which can allow increased light energy from a light source to be directed to a given space or area over that which is generally possible with a conventional single fixture. The invention also allows spreading of the light energy of a light source, or other manipulation and reconfiguration of the light energy.
A still further object of the present invention is to provide a means and method as above described which allows a wide variety of flexibility and options with regard to controlling light.
Another object of the present invention is to provide a means and method as above described which is generally as economical or more economical than conventional systems.
Another object of the present invention is to provide a means and method as above described which can produce very beneficial results regarding glare control and spill light control.
A still further object of the present invention is to provide a means and method as above described which can allow for significantly different placement of light sources than conventional systems with resulting benefits to lighting to the target space or area, spectators, television coverage, or persons outside the target area.
Another object of the present invention is to provide a means and method as above described which provides improved and beneficial lighting for visual tasks for participants and events within a lighted target area, for example car drivers or players, as well as beneficial lighting for spectators, video requirements of television, film requirements for still photography, and motion picture film, and which minimizes spill and glare light for persons outside the target who are visually impacted by the lighting.
Another object of the present invention is to provide a means and method as above described which can produce lighting for a large target area which can be controlled as to adequate quantity, level, uniformity and smoothness across the entire area or volume, and predictably controls shadows or varying intensity areas for modeling effect, such as might be desired.
These and other objects, features, and advantages of the present invention will become more apparent with reference to the accompanying specification and claims.